1. Field
The present invention relates generally to cellular communication systems, and more specifically, to a method and apparatus for managing uplink resource allocation in a communication system.
2. Background
Global System for Mobile Communication (GSM) cellular communication systems provide communication services to mobile and portable devices through an arrangement of base stations. In GSM systems, frames of timeslots and radio blocks are transmitted and received at the mobile station using time division multiplexing. GSM systems have evolved from providing strictly voice services to also providing data services. Standards such as general packet radio service (GPRS) and Enhanced Data fro Global Evolution (EDGE) further define the protocols for data communication within GSM based systems. The access terminals, also sometimes referred to as mobile devices, portable devices and by other names, are categorized into classes where the classes are at least partly based on the number of simultaneous timeslots that the access terminal can use in the uplink and the downlink directions. Multi-slot classes represent the capabilities of an access terminal to receive/transmit and process multiple timeslots of a frame. During Dual Transfer Mode (DTM), transmitted and received frames include circuit switched calls timeslots including information related to voice calls (or other circuit switched calls) and data timeslots that include information related to data. In conventional GSM EDGE Radio Access Network (GERAN) systems, access terminals categorized within some higher multi-slot classes can transmit and receive data as well as voice information using multiple timeslots within of frame.
Uplink Status uplink status flags (USFs) provide a mechanism for the base station to dynamically allocate uplink timeslots assigned to an access terminal. The USFs are transmitted in the downlink and identify the uplink timeslots that are authorized for use by the access terminal. A USF in a downlink timeslot indicates that the access terminal is authorized to transmit on the corresponding uplink timeslot in the next frame. GERAN specifications such as 3GPP TS 44.060, 3GPP TS 45.002 and 3GPP TS 43.055 attempt to define the downlink timeslots that should be monitored for USFs. Unfortunately, the GERAN specifications are ambiguous for some situations where DTM and High Multi-shot Classes are applied.
Therefore, there is need for an apparatus and method for monitoring uplink status flags in a GSM communication system.